It’s not a beautiful word, localism, but it’s an ideal with whose basics it is hard to disagree: that local residents and businesses should have a say in what happens to their communities, and that decisions on things such as planning should, where practical, be devolved to local government. It is one of the few remnants of David Cameron’s “big society” that is still breathing any sort of life.

Cameron and his party also love Tech City, the area of east London that is a buzzing hive of entrepreneurial electronic endeavour. So when the businesses of Tech City and local residents combine to oppose a property development that does little or nothing for them except harm, and propose a viable alternative, and when a local authority is engaged in constructive conversations with the site’s developers that might lead to a better outcome, we are, surely, in Tory heaven.

This, however, is to reckon without the Tory mayor of London, Boris Johnson, who unilaterally declared that he is “strongly supportive” of the proposed building of seven towers on Bishopsgate Goodsyard, and that with a few adjustments he would give it permission, no matter what the local authority might think. Which undermines the latter, and puts to an end the patient dialogue taking place until now. So much for localism.

The 11.6-acre site is one of the largest left in central London, a piece of redundant Victorian railway infrastructure that is partly listed, a thick sliver running eastward from the edge of the City, through the territories of the boroughs of Hackney and Tower Hamlets, and crossed by the hipster high street of Brick Lane. The proposal, by a joint venture of Hammerson and Ballymore, is of a kind now familiar in London: a row of towers stuffed with luxury housing. At their highest they will reach the level of the Gherkin or the Walkie Talkie.

It is better than some such proposals, to the extent that it offers something more than a wasteland of Chinese granite at its base. A preserved section of brick viaduct will be converted into a shopping area, with a small park on top designed by some local architects. When it comes to placebo greenery, this is more convincing than the Walkie Talkie’s “Sky Garden” or the urban parsley of the Garden bridge. It will, however, thanks to the proposed towers, be cast into shadow on late summer afternoons, which is when it is most likely to be in use.

The Tech City people oppose it because it offers little of the kinds of flexible space that small- and medium-sized enterprises need, and disrupts the “cluster” effect – the benefits of having many businesses in close proximity on which they thrive. Conservationists oppose it because the towers will crash into views down Victorian and Georgian streets in neighbouring conservation areas, because the design of the new work is could-be-anywhere generic, and because the relationship of the new to the old is clumsy. Local residents oppose it because it will cast a slab of shadow hundreds of yards to the north, including on the 1890s Boundary estate. This is poignant: the estate was a world-leading pioneer of council housing, whose charming arts-and-crafts architecture was based on maximising daylight to its homes, whose light will now be reduced.

As it currently stands, the development is unlikely to have more than 10% of its units as affordable housing, which is well below the usual rate of 33% or so. The developers plead that the complexities of the site, which includes a working section of the London overground railway, make it unprofitable to offer more, or to reduce the bulk of their towers. They cite as evidence the financial viability assessment they produced as part of their planning application which, as usual in such cases, is kept from public view. So we have to take their word for it.

All the opponents agree that the proposed development has nothing to do with the area, that it will sterilise and not vitalise. Tower Hamlets has not yet expressed a view, but Jules Pipe, the elected mayor of Hackney, says that “this scheme is completely unsuitable for this part of Shoreditch. The towers are on a vast scale and would damage the whole local environment. The housing provided would be luxury accommodation, to be bought mostly by overseas investors, and would do nothing to alleviate London’s housing crisis. The scheme does not provide enough, or the right kind of, employment space.”

There is, in other words, nothing truly local about it. For Johnson, however, it is “slender and elegant”. He has, it is true, proposed some changes. He wants the height of the tallest towers to come down, which won’t make a huge difference to the overall impact and overshadowing. He wants more affordable housing, but as he defines “affordable” as 80% of market value, and as many of the units here will be worth seven-figure sums, this is not much comfort for low-income locals looking for a home.

His case would be stronger if there were no alternative. But the architect Gensler, whose London office is nearby, has volunteered an alternative scheme that shows how the site can be profitably developed without a phalanx of towers. Gensler is itself a multinational commercial company, so it should know something about viability. But Johnson’s intervention means that its thinking, except in some small ways, will have little impact.

It’s hard to know why Johnson would want to do this, except to cross a few more hundred units off the housing targets he has set himself. Which, as these units will do little to address London’s actual housing needs, is pointless. Johnson has also made plain his desire for investment, which is fine, but he doesn’t seem to care for whom, by whom and for what benefit this investment is made.